This invention relates to a muting circuit in combination with a tape recorder which is detachably attached to an audio instrument, e.g. car stereo and home stereo apparatus.
A muting circuit is included in, for example, the reproduction or playback circuit of a tape recorder for breaking the signal transmission when desired signals are not handled. The muting circuit serves to permit transmitting musical signals, etc. only when the tape deck is set in the playback mode. If a muting circuit is not provided, a click noise is generated in switching of the playback mode. Also, noise, of the amplifier system is reproduced during the stop mode. In general, an attenuator circuit consisting of a resistor and a switching bipolar transistor connected in series with the resistor is used as a muting circuit. In the conventional muting circuit of this type, the switching transistor is rendered conductive by supplying a base current to the transistor for performing the muting function, i.e., for breaking the signals.
The conventional muting circuit described above gives rise to inconveniences when used in a tape recorder-reproducer in which the recording-reproduction amplifier system including the main portion of a muting circuit, and the tape deck system including a switching circuit serving to issue muting instructions are systematized or fabricated independently. Specifically, the muting function can not be performed if the tape deck is detached from the amplifier, resulting in that the noise of the amplifier is directly reproduced from the loudspeaker.